I'm sure someone will answer this but before I read on the word "concrete" proof stands out.
There is a difference between "concrete" (real, substantial) proof and DOCUMENTED (as in investigation) proof. This can be a problem with DCF especially in Florida. We all know from sad past events that investigators do not document everything and make lots of mistakes, some of which have included returning kids to very bad parents and ending up in deaths.
Personally, I get fed up with semantics. Those of us who are struggling to be non-judgemental and fair and balanced still can't ignore the elephant standing in the corner no matter how many people say "whatever you do, don't look at that elephant".
Whether DCF was ever called or not (and if they weren't, shame on people who didn't want to get involved), DT put her children at risk. If you have children and you have to work, you make arrangements for them to be properly cared for. There are plenty of free or low cost after school programs available in Florida. I don't know how much money DT made to supplement the $40,000.00 per year that her live-in makes. Apparently she usually got off work about 4:00 p.m. Arrangements for that time period would not be costly. She noted in one interview that the neighborhood was so safe she could "fall asleep with the garage door open and t.v.s and stuff out there and never think twice about it" (paraphrased). Her seven year old daughter consistently ran off (for what reason - she had some problems) and remained at various places depending on who is doing the talking: searching for people to play with, climbing trees, hanging out by water, etc., etc., and DT KNEW about it because as we know she had a list of people to call. And I don't care what people say is the reason she flubbed it, she stated right on t.v. that Somer had never, never done this before. A lonely, frustrated child about who in hindsight mom wistfully said, "well....she was picked on a lot".
This says that rather than take responsibility for her kids, she left it up to the good will or availability of others. Depending on the day, it could be neighbors, babysitters (who quit because of the stress of worrying about a missing child), male friends, or a 10 year old. Please show me where a 10 year old babysitting is acceptable? Did the 10 year old have a key or was the house usually left open? To whom? This site and many others have debated DT's role in this tragedy since it happened. So again, the facts. These are her children. It was her responsibility to care for them or find someone trustworthy to provide care in her absence. The children were left with a variety of people or no people, and dealt with a variety of males coming in and out of the mother's life. This child had problems. She ran away but always came back. Not this time. She was killed. The killer knew this child was running loose. Whose fault was it? Not the bus system, and not the poor 10 year old who will carry this burden for the rest of her life.
Neglect. The word signifies not carrying out a responsibility. In this case, it is appropriate. Whether DCF said it or says it now, it is clear.